Rotary hook for sewing machines



April 2, 1963 L. J. KUHAR 3,083,659

ROTARY HOOK FOR SEWING MACHINES Filed Dec. 19, 1960 IN VENTOR. LUDWIG J. KUHAR TORNE Y United rates Patent 3,083,659 ROTARY 1100K FUR SEWING MAQ WES Ludwig J. Kuhar, Clark, N.J., assignor to The Singer Manufacturing Company, Elizabeth, N.J., a corporation of New Jersey Filed Dec. 19, 1960, Ser. No. 76,618 Claims. (Cl. 112228) The present invention relates to rotary hooks for sewing machines.

It is an object of this invention to provide a rotary hook for use with high speed sewing machines, that is, sewing machines designed for operation at sewing speeds in the neighborhood of 6000 stitches per minute. More particularly, the present invention is directed specifically to the provision of an economical and effective means for preventing overheating of the hook and which, at the same time, will prevent the accumulation of lint about the bobbin case carrier and will also provide a smooth path for the passage of the thread loop about the bobbin case carrier.

It is also an object of this invention to provide in a rotary hook a simple and economical means for efiectively removing lint from the hook and preventing accumulation of lint that would interfere with loop formation.

Having in mind the above and other objects that will be evident from an understanding of this disclosure, the invention comprises the devices, combinations and arrangements of parts as illustrated in the presently preferred embodiment of the invention which is hereinafter set forth in such detail as to enable those skilled in the art readily to understand the function, operation, construction and advantages of it when read in conjunction with the accompanying drawings in which:

FIG. 1 is a fragmentary sectional view of a sewing machine embodying the present invention and illustrating the rotary hook in front elevation.

FIG. 2 is a rear elevational view of the hook illus 'trated in FIG. 1.

FIG. 3 is a fragmentary side elevational view of the hook illustrated in FIG. 1.

FIG. 4 is an enlarged fragmentary detail sectional view taken substantially on the line 44 of FIG. 1.

FIG. 5 is a detail perspective view of the gib per se of the hook illustrated in FIG. 1.

FIG. 6 is an enlarged fragmentary top plan view of the hook illustrated in FIG. 1.

FIG. 7 is a view similar to FIG. 6 but with the loopseizing beak of the hook in loop-seizing position.

With reference to the drawings there is illustrated a fragmentary portion of a sewing machine bed 1 which forms a part of the frame of a sewing machine. The bed 1 is provided with a throat plate 2, the upper surface of which forms a part of the work supporting surface of the machine. A needle 3 is adapted to penetrate work W on the throat plate 2, thereby defining the point of stitch formation, and to penetrate the throat plate 2 through a needle aperture 4. Beneath the throat plate 2, the needle 3 cooperates with a rotary hook 5 in the formation of lock stitches, the hook 5 being mounted upon the end of a rotary hook shaft 6 journaled in the bed.

The hook 5 comprises a cup-shaped hook body 7 having a hub portion 8, an end wall 9 extending laterally from the one end of the hub portion, and a peripheral sidewall 10 carried by the end wall 9 on the side opposite from the hub portion 8 and terminating in a free edge 11. The hub portion 8 is provided with a bore 12 for receiving the end of the hook shaft 6 and which is secured therein by set screws 13. The hook 5 is thus carried by and rotates with the hook shaft 6 about the axis 5 of the shaft 6, and in the usual manner is designed to make two complete revolutions for each reciprocation of the needle 3. A

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loop seizing beak 14 is formed in the side wall 10 of the hook body 7, the beak 14 including a loop seizing point 15 at the free edge 11 of the side wall 10 and a loop expanding edge 16 that, from the point 15 toward the end wall 10, is inclined rearwardly relatively to the direction of rotation of the hook, which is indicated by the arrow R. In the formation of the beak 14, a portion of the side Wall 10 is completely cut away to form a gap therein, with the beak 14 at edge of the gap and a free edge 17 at the other edge of the gap. A portion of the end wall '9 is also cut away to the edge 18 which provides clearance for thread handling. The edge 18 merges with the loop expanding edge 16 of the beak 14 at a throat 19.

The hook 5 is provided with an internal circular raceway 20 that is coaxial of the axis of the hook shaft 6. The portion of the raceway 20 in the area beginning with the edge 17 and extending for about one hundred and fifty degrees in the direction away from the beak 14, is formed in the free edge of the side wall 10 and has an open outer side. A gib 21 is secured to the side wall 10 by screws 22 and includes an inwardly directed flange 23 having an edge 24 that constitutes a continuation of the outer side wall of the raceway 20 and thus closes the open side of the raceway. The gib 21 is also formed with a loop controlling tail 25 spaced angularly from the beak 14. The usual thread guard 26 is also secured to the pheriphery of the side wall 10. A bobbin case carrier .27 has a cylindrical sidewall 28 upon which there is a discontinuous peripheral bearing rib 29 journaled in the raceway 20 for mounting the same within the hook body 7 for rotation of the hook relatively to the bobbin case carrier. The opposite ends of the bearing rib 29 comprise a loop detaining shoulder 30 and a loop confining shoulder 31. The side wall 28 is formed with a needle aperture 32 through which the needle 3 penetrates at the extreme downward position of its stroke. The needle 3 and thus the needle aperture 32 defines the loop seizing position of the hook 5. The needle 3 divides the bobbin case carrier 20 diametrically generally into a cast-on side and a cast-off side. On the top or free edge of the side Wall 28 on the cast-oil side there is a laterally extending loop controlling flange 33 that extends slightly beyond the loop seizing position defined by the needle 3 and has a notch 34 in the face thereof for receiving a rotation restraining finger 35. Mounted within the bobbin case carrier 27 is a bobbin case 36 which in turn carries a bobbin 37.

The inner face of the loop controlling flange 33, that is, the face adjacent to the bearing rib 29, is disposed closely adjacent to the path of travel of the loop seizing point 15 of the hook except at the point of stitch formation. At this point, the flange is provided with a clearance 38 to permit the needle to pass between the flange and the path of travel of the point 15.

A series of holes 3? are formed in the hook body 7. The holes 3% are spaced circumferentially about the hook 7 in the area opposite from the beak 14 and are formed partly in the end wall 9 and partly in the side wall 18. The holes are made as large as possible consistent with leaving Webs of adequate thickness from the standpoint of strength between the holes. Each of the holes 3% are divergent outwardly and are formed on an axis A which, from the free end of the side wall 10 toward the hub 8, are inclined outwardly (FIG. 4) relative to the axis 5 of the hook and are inclined rearwardly (FIG. 6) relatively to the direction of rotation R. Thus, upon rotation of the hook, air is circulated outwardly through the holes 39 as is illustrated by the arrows C in PEG. 3. This circulation of air will cool the hook 5 and will also remove lint that tends to accumulate in the hook. By forming the holes 39 as shown, there is also provided a smooth path for the loop of needle thread as it passes between the back of the bobbin case carrier 27 and the end wall 9 of the hook body. In other words, by inclining the holes- 39 in a direction opposite to the direction of rotation, there are presented no obstructions upon which the loop of thread can be caught.

The removal of the material in the formation of the holes 39; unbalances the hook. To rebalance the same dynamically, there is provided on the gib 21 an enlargement 49 of the flange 23. Specifically, the enlargement 40 extends in a direction axially of the hook and has a top surface 41 which is disposed closely adjacent to the pathof travel of the loop seizing point 15; and thus, closely adjacent to the inner face of the loop controlling flange present, tends to. accumulate particularly about the needle aperture 32 in the bobbin case carrier 27 and to form a relatively hard mass M'. The normal result of this accumulation is illustrated in FIG. 4. As illustrated in this view, the mass M tends to build up against the flange $3 and on the wall 28. of the bobbin case carrier until eventually the-re is completely solid mass except for small aperture that is kept open bythe needle. The needle threadN'extends from the supply, down the long groove side and through the eve of the needle 3, and upwardly to the last stitch'in the work W. As illustrated at X in FIG. 4, the loop seizing point 15 of the hook passes on and closely adjacent to that side of the needle on which thelimb of the needle thread N extends upwardly to 'the work W. I In order to effect loop seizure, a loop must be formed in this limb of the needle thread N, which loop is normally formed by the rise of the needle 3 coupled with the frictional resistance between the thread N and the work W which prevents the thread from rising with the needle. With the, accumulation of the mass M about the needle, the thread N cannot throw a loop properly for entrance by the point 15 of the beak 14. The result is skipped stitches.

As illustrated, in FIG; 6, the enlargement 49 of the gib21effectively prevents interference with loop formation by the accumulation of the mass M by virtueof the fact that the top surface 41 thereof, which is disposed substantially in the path of travel of the point 15 and extends substantially into contact with the side wall 28 of the bobbin case carrier 27, will dislodge any accumulation on the side of the needle 3 adjacent to the path of travel of the pohit 15, which is the side upon which the loop is formed. Any accumulation in the space between the surface 41 and the needle 3 is necessarily so small that it can be effectively cleared by the action of the thread N.

Numerous alterations of the structure herein disclosed will suggestthemselves to those skilled in the art. However, it is to be understood that the present disclosure relates to a preferred embodiment of my invention which is for purposes of illustration only and not to be construed as a limitation of the invention. All such modifications which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims.

Having thus described the nature of the invention, What I claim herein is:

' l. A rotary hook for sewing machines comprising a cup shaped hook body including a hub, an end wall extending laterally from said hub, and a peripheral side wall carriedby said end wall and having a free edge,

said side wall having a gap and a loop seizing beak formed on said side wall at one edge of said gap, said beak terminating in a loop seizing point at the free edge of said side wall and including a loop expanding edge which, from said point toward said end wall, is inclined rearwardly relatively to the direction of rotation of said hook, said side wall having an internal circular raceway, a bobbin case carrier having a peripheral bearing rib journaled in said raceway for rotation of said hook relative to said bobbin case carrier, said hook body having a plurality of holes, each of said holes being formed partly in said end wall and partly in said side wall and having an axis, which, from the free edge of said side wall toward the hub of said hook, is inclined both outwardly away from the axis of the hook and rearwardlyrelativelyto the direction of rotation of the hook, thereby circulating air outwardly through said holes during rotation of' said hook. i

2. A rotary hook for sewing 'machines comprising; a cup-shaped hook body including a hub, an end wall extending laterally from said' hub, and a peripheral side wall carried by said end wall and having a freeedge, said side wall having a gapoan d a loop seizing beak formed on said side wall at one edge of said gap, said beak terminating in a loop seizing point at the free edge of said side wall and including a loop-expanding edge which, from said point toward said end wall, is inclined rearwardly relatively to the direction of rotation of saidhook, said side wall having an internal, circular-raceway of which the portion adjacent to said gap on the side opposite from said loop seizing beak is formed in the free edge of said end wall and has an open side, a gib secured to the periphery of said side wall and having an inwardly directed flange closing the open side of said raceway, a bobbin case carrier having a peripheral bearing rib journaled in said raceway for rotation of said hook relative to said bobbin case carrier, means for circulating air through said hook during rotation of said hook comprising a plurality of inclined holes in said hook body, each of said holes being formed partly in said end wall and partly in said side wall, and a counterweight on said gib for dynamically balancing said hook.

3. A rotary hook for sewing machines comprising a cupashaped hook bodyv including a hub, an end wall. extending laterally from said hub, and aperipheral side wall carried by said end wall and, having afree edge, said side wall having a gap, a loop seizing beak formed on said side wall atone edge of said gap, said. beak terminafine in a p zi po nt: at he free ed Q i aid' s e l and n lu n a o p x an in edge. whi from said point toward said; end; Wall, is inclined rearwardly relatively to the direction of rotation of said hook,

said point defining a circular opath of travel upon rota-.

tion of said hook, said side wall having an internal circular raceway of which the portion adjacent to said gap on the side opposite from saidloop seizing beak is formed in the free edge of saidendwall and has an open side, a bobbin case carrier received Within said hook bodyoand having a peripheral side wall, a peripheral bearing rib on the side wall of said bobbin case carrier and journaled in said raceway for rotation of said hook relatively to said bobbin case carrier, the side wall of said bobbin case carrier having a needle aperture disposed closely adjacent to the path of travel of said loop seizing beak and defining aloop seizing position, a laterally extending loop controlling flange, on the side wall of said bobbin case carrierand disposed in spaced. relation to the path of travel of theloop seizing point toprovideneedle clearance between said flange and said loop seizing point, a gib, secured to the periphery of said side wall andhaving an inwardly directed flange closing the open side of said raceway and terminating in a, free edge. adjacent to the side wall of said bobbin case carrier, said gib having a portion of said flange disposed substantially in. the plane defined by the, path. or" travel of said loop seizing point.

4. A rotary hook for sewing machines in accordance with claim 3 in which the portion of the gib disposed substantially in the plane defined by the path of travel of said loop seizing point comprises an enlargement of said flange to provide a counterweight for dynamically balancing said hook.

5. A rotary hook for sewing machines in accordance with claim 4 in which said hook body has a plurality of holes, each of said holes being formed partly in said end wall and partly in said side Wall and having an axis which, from the free edge of said side wall toward the hub of References Cited in the file of this patent UNITED STATES PATENTS 1,596,487 Hohmann et a1 Aug. 17, 1926 1,928,590 Grieb Sept. 26, 1933 1,970,428 Myers Aug. 14, 1934 

2. A ROTARY HOOK FOR SEWING MACHINES COMPRISING A CUP-SHAPED HOOK BODY INCLUDING A HUB, AN END WALL EXTENDING LATERALLY FROM SAID HUB, AND A PERIPHERAL SIDE WALL CARRIED BY SAID END WALL AND HAVING A FREE EDGE, SAID SIDE WALL HAVING A GAP AND A LOOP SEIZING BEAK FORMED ON SAID SIDE WALL AT ONE EDGE OF SAID GAP, SAID BEAK TERMINATING IN A LOOP SEIZING POINT AT THE FREE EDGE OF SAID SIDE WALL AND INCLUDING A LOOP EXPANDING EDGE WHICH, FROM SAID POINT TOWARD SAID END WALL, IS INCLINED REARWARDLY RELATIVELY TO THE DIRECTION OF ROTATION OF SAID HOOK, SAID SIDE WALL HAVING AN INTERNAL CIRCULAR RACEWAY OF WHICH THE PORTION ADJACENT TO SAID GAP ON THE SIDE OPPOSITE FROM SAID LOOP SEIZING BEAK IS FORMED IN THE FREE EDGE OF SAID END WALL AND HAS AN OPEN SIDE, A GIB SECURED TO THE PERIPHERY OF SAID SIDE WALL AND HAVING AN INWARDLY DIRECTED FLANGE CLOSING THE OPEN SIDE OF SAID RACEWAY, A BOBBIN CASE CARRIER HAVING A PERIPHERAL BEARING RIB JOURNALED IN SAID RACEWAY FOR ROTATION OF SAID HOOK RELATIVE TO SAID BOBBIN CASE CARRIER, MEANS FOR CIRCULATING AIR THROUGH SAID HOOK DURING ROTATION OF SAID HOOK COMPRISING A PLURALITY OF INCLINED HOLES IN SAID HOOK BODY, EACH OF SAID HOLES BEING FORMED PARTLY IN SAID END WALL AND PARTLY IN SAID SIDE WALL, AND A COUNTERWEIGHT ON SAID GIB FOR DYNAMICALLY BALANCING SAID HOOK. 